Electrophotographic imaging processes employ a photoconductive element comprising an insulating photoconductive layer disposed on an electrically conductive support. Photoconductive layers have in the past contained various inorganic photoconductors such as amorphous selenium, cadmium sulfide or lead oxide or organic photoconductors such as polyvinyl carbazole and aryl amine compounds. While many of the common photoconductors have good electrophotographic sensitivity in the wavelength range from ultraviolet to red, their sensitivity in the near infrared range above about 700 nm is not sufficiently high for use with diode lasers which currently are of great importance in recording techniques.
In lieu of the more commonly used photoconductors it has been suggested that certain metal phthalocyanines which absorb in the near infrared region be employed. For example, U.S. Pat. No. 4,426,434 suggests a photoreceptor having an evaporated film of chloroaluminum phthalocyanine or chloroaluminum monochlorophthalocyanine. It is said that such compounds have high photosensitivity in the near infrared region. Unfortunately, such compounds, as well as many other phthalocyanines, evidently are not readily dispersible in coating formulations and, to deposit them as photoconductive layers, the expensive procedure of vacuum evaporation must be used.
The patent to Tanikawa, U.S. Pat. No. 4,458,004 dated July 3, 1984 discloses an optical recording medium containing a fluorine-substituted pthalocyanine. A structural formula in the patent shows a central symbol M which is said to represent, among many other things, titaium oxide. The patent does not suggest, however, that any of the indicated phthalocyanines are photoconductive or that they can be dispersion coated to form photoconductive layers of low granularity. No method of preparation of the phthalocyanines is mentioned.